1. Field of the Invention
The present invention relates to a driving device using an electro-mechanical conversion element.
2. Description of the Related Art
Hitherto, a driving device employing a piezoelectric element (electromechanical conversion element), which is used to drive a lens of a digital camera or a camera phone, has been known. Such a driving device is configured so that one of end portions in the expansion/contraction direction of the piezoelectric element is fixed by a platform, and that a shaft-like driving frictional member extending in the expansion/contraction direction of the piezoelectric element is fixed to the other end portion of the piezoelectric element. A frictional engagement member capable of moving along the driving frictional member is mounted on the circumferential surface of the driving frictional member by being inserted thereon. The lens serving as a driven member is attached thereto through the frictional engagement member.
In such a driving device, the piezoelectric element is expanded or contracted by applying a pulse-like voltage to the piezoelectric element. Thus, the driving frictional member moves. In a case where the piezoelectric element deforms at a low rate, the frictional engagement member moves together with the driving frictional member. In a case where the piezoelectric element deforms at a high rate, the frictional engagement member remains located at the same position due to inertia of the masses of the frictional engagement member and the driven member, whereas the driving frictional member moves. Therefore, the frictional engagement member frictionally engaged with the driving frictional member intermittently moves with fine pitches. Thus, the lens attached to the frictional engagement member can be moved (see, for example, JP-A-2002-142470).
However, in this related driving device, it is difficult to position the electromechanical conversion element and the driving frictional member with good precision. Also, when the deviation of the position of the driving frictional member with respect to the electromechanical conversion element occurs, it is difficult to move an object, which is to be moved, with good precision.
Also, in a case where an impact is applied to the related driving device due to the dropping thereof, a bonded portion between the electromechanical conversion element and the driving frictional member may be damaged.